Directional AF Cooperative Communication System Based on Outage Probability

Introduction

Basic idea of cooperative communication is, in multi-user communication environment, using each adjacent mobile node of single side antenna to send the signal cooperatively by sharing the antenna each other according to a certain method so as to produce a kind of virtual environment similar to multi-antenna transmission, gain space diversity gain and enhance transmission property of system. The working achievement is as shown in Figure 1. As the research topic in recent years, cooperative communication has gained many stage achievements (Al-Jumeily, 2015, pp. 122-129 and Arase, 2011, pp. 18-29 and Barbosa, 2015, pp. 89-99 and Puzar, 2011, pp. 137-150 and), which mainly focus on: cooperative mode, capacity problem, network code, system synchronism, relay node selection, resource management, etc. Early in 1970s, Van has proposed, tri-terminal channel and deduced the upper and lower bound of the channel capacity (Vander, 1971, pp. 120-154), but cooperative communication, as a kind of diversity technique, was proposed clearly at the beginning of this century (Laneman, 2004, pp. 3062-3080 and Hunter, 2002, pp. 118-122). Laneman et al firstly proposed a concept of two-stage synchronous transmission and gave the two currently common relay modes, namely amplify-and-forward and decode-and-forward (Nasipuri, 2000, pp. 1214-1219). The Literature also showed several kinds of reinforced relay modes, such as self-adaption relay and reinforced relay, etc. In the same period, Hunter also proposed a similar cooperative diversity protocol (Hunter, 2002, pp. 118-122), in whose model, relay cannot only forward source node information, but also sends its own information. From then on, cooperative communication technology received attention from academic world and many research achievements were also published successively (Bletsas, 2007, pp. 3450-3460), but all these researches base on omnidirectional antenna. Directional antenna is able to focus on sending the energy to the direction needing communication so as to reduce the signal interference in non-communication direction, increase spatial multiplexing of channel and enhance the capacity of channel, so it has wide application prospects. Also, many scholars have carried out large quantity of researches on related contents (Geletu, 2011, pp. 163-164), and complete communication system using directional antenna (Laneman, 2002, 3062-3080 and Ramanathan, 2005) has generated. In military field, directional antenna is more widely applied, especially in the occasion where RF (Radio Frequency) invisibility shall be considered, such as stealth fighter, the advantage of directional antenna is obvious and it has become the sole selection of the realization of communication and radar system. The researches on directional antenna and cooperative communication are very rich, but the researches on combination of them are fewer (Li & Tan, 2016, pp. 497-503).